Many systems have multiple components that wear at different rates and are replaced as they wear out in order to keep the whole system operating. In such systems the replacement of some or all worn out components may require specially trained service professionals such as field service engineers. Some systems may be provided with replaceable components that are replaceable by the system operator, thereby eliminating, or at least reducing the frequency of, the need to place a service call. This not only may reduce overall maintenance costs, but also reduces system down time by eliminating response time. In either case, replacement by a service call or by the operator, it is desirable to track the usage of replaceable components so as to accurately anticipate when they will fail. U.S. Pat. No. 6,718,285, issued in the name of Schwartz, et al., issued on Apr. 6, 2004, henceforth referred to as the Schwartz patent, discloses a replaceable component life tracking system and is hereby incorporated in this application by reference.
The Schwartz patent discloses a replaceable component life tracking system in which the usage of each replaceable component is tracked using a predetermined parameter. In a preferred embodiment, the system is a printing device and the usage of each replaceable component is tracked using the parameter corresponding to the number of pages printed. The life expectancy of each replaceable component is predetermined, and as the usage of each replaceable component is tracked, it is compared to the predetermined life expectancy, and the result periodically reported to the system operator via an operator interface. If any replaceable component usage reaches the life expectancy of that replaceable component, the operator is notified immediately, and instructed that the replaceable component ought to be replaced.
For most systems, for a number of reasons, a life tracking process of the type described above only provides an approximate forecast of the end of useful life of the replaceable components. For example, the wear rate of some or all of the replaceable components may not be constant with respect to the predetermined usage parameter. In the printing device embodiment, for example, all printed pages do not necessarily result in the same wear rate for all replaceable components. Furthermore, if the system is one that stops and starts between jobs, wear of the replaceable components may be occurring, but with no incrementing of the usage parameter. It is well known that in systems of this type the components wear faster when many shorter jobs are being run versus fewer longer jobs. Also, most replaceable components do not fail instantaneously due to wear, but rather tend to degrade gradually.
As a result of these observations, the decision of when to replace a component as its usage approaches or exceeds the life expectancy is left to the system operator. Furthermore, the operator may be willing to accept some degradation of system performance and therefore replace components less frequently thereby decreasing operating costs. In the printing device embodiment, image quality on the printed pages may degrade slowly and, if the images being printed are less demanding textual images versus pictorial images for example, or if the customers are less demanding, the operator may choose to continue to use a component well past the life forecasted by the life tracking process.